Generating travel time data

ABSTRACT

The generation of travel time data is disclosed in which coordinates are received for a starting location ( 1901 ). A maximum travel time is received ( 1903 ) and processed graph data is read that includes nodes representing pre-filtered map features and edges representing travel times between nodes. A temporary graph is built ( 1907 ) of selected nodes that can be reached via selected edges within the maximum travel time. Candidate destinations are received ( 1908 ) and the travel time to these candidate destinations is tested ( 1909 ) with reference to the temporary graph.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from United Kingdom patent application11 22 383.1, filed Dec. 23, 2011, the entire disclosure of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of generating output dataidentifying travel times from a starting location to candidatedestinations. The present invention further relates to a data outputgenerating apparatus for generating output data identifying travel timesfrom input data consisting of a starting location and candidatedestinations.

2. Description of the Related Art

In addition to representing journeys in terms of distances, it is alsoknown to describe such journeys in terms of the time that would betaken, possibly using various forms of transport. It is also known toproduce maps with isochrones, showing locations that have a similartravel time, irrespective of geographical distance. However, these donot facilitate the ranking of candidate destinations in terms of theirtravel times. Existing technical solutions also present problems interms of calculating travel times using available processingcapabilities in real time.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided amethod of generating travel time data, comprising the steps of:receiving coordinates from a starting location; receiving a maximumtravel time; reading processed graph data comprising nodes representingpre-filtered map features and edges representing travel times betweensaid nodes; building a temporary graph of selected nodes that can bereached via selected edges within said maximum travel time; receivingcandidate destinations; and testing the travel time to said candidatedestinations with reference to said temporary graph.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an environment in which the present invention may beimplemented, including mobile devices;

FIG. 2 details a mobile device identified in FIG. 1;

FIG. 3 show a protocol diagram illustrating operations performed withinthe environment of FIG. 1;

FIG. 4 shows operations performed by the enhanced server 109;

FIG. 5 illustrates data defining the details of a map;

FIG. 6 shows the map data of FIG. 5 as a more conventional looking map;

FIG. 7 shows procedures for processing the map data of FIG. 5;

FIG. 8 shows the map of FIG. 6 with features removed;

FIG. 9 illustrates a graph data-set;

FIG. 10 details procedures for performing a search;

FIG. 11 shows the graph of FIG. 9 within a bounded region;

FIG. 12 shows the region of FIG. 11 further subdivided;

FIG. 13 shows the regions of FIG. 12 further subdivided;

FIG. 14 shows the regions of FIG. 13 further subdivided;

FIG. 15 shows the regions of FIG. 14 further subdivided;

FIG. 16 shows the regions of FIG. 15 further subdivided;

FIG. 17 illustrates an example of a binary space partitioning tree datastructure;

FIG. 18 shows a table associating nodes with regions;

FIG. 19 illustrates procedures for performing a search;

FIG. 20 shows procedures for judging the acceptability of a startlocation, identified in FIG. 19;

FIG. 21 shows procedures for building a temporary graph as identified inFIG. 19;

FIG. 22 shows an example of temporary graph;

FIG. 23 shows procedures for determining whether a candidate destinationmay be accepted as identified in FIG. 19; and

FIG. 24 shows a graphical display of an improved isochronalrepresentation.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1

Recent technical advances have improved the way in which largequantities of data may be searched to produce information that may beco-ordinated over a network to provide results to a user. Increasingly,these results may be conveyed to mobile devices; whereby the overallsystem allows a user to make informed decisions in real-time.

In the environment of FIG. 1, user mobile devices 101, 102, 103, 104 and105 are shown communicating over a network 106 with a first serviceprovider server 107 and a second service provider server 108. Server 107provides, in this example, a first service showing first entity typesranked according to preferences defined by a user. Similarly, server 108provides a second service showing second entity types also rankedaccording to preferences defined by a user. These preferences mayinclude distances from a specified starting location. However, bydeploying an embodiment of the present invention, it is possible forrankings defined in terms of distances to be replaced by rankingsdetermined by travel times.

To achieve rankings defined in terms of travel times or journey times,data relating to a specific journey may be read from a service enhancingserver 109. In this embodiment, end users 101 to 105 do not communicatewith the service enhancing server 109 directly; the provision of journeytime related data (as distinct from distance data) is provided to theprimary service providers 107, 108 etc as a procedure for enhancing theservice that they provide.

In an embodiment, the server computer 109 is configured to generatetravel time data. It has a processor that is configured to receivecoordinates starting location; receive a maximum travel time; readprocessed graph data comprising nodes representing pre-filtered mapfeatures and edges that include representations of travel times betweensaid nodes. It is also configured to build a temporary graph of selectednotes that can be reached via selected edges within the maximum traveltime, receive candidate destinations and test the travel time to thecandidate destinations with reference to the temporary graph.

In an embodiment, the processor of the server computer 109 is alsoconfigured to divide a geographical region repeatedly so that eachdivided region includes one exclusive graph node and thereby create atwo-dimensional binary space partitioning tree. The starting location istranslated to the location of graph node by making reference to thetwo-dimensional binary space partitioning tree. Each candidate locationis then tested upon arrival with reference to the two-dimensional binaryspace partitioning tree.

In an embodiment, the server computer 109 also includes a cache suchthat the cache is configured to store a previously built temporary graphto facilitate repeated searches from the starting location but fromdifferent candidate destinations.

In an embodiment, program applications are downloaded to mobile devices101 to 105 such that, when executing, the mobile device is configured toreceive travel time data from the server computer 109.

In an embodiment, the mobile devices also include components forgenerating location data representing the location of the mobile device,wherein the location data is conveyed computer to identify startinglocation.

FIG. 2

Mobile device 101 is detailed in FIG. 2, having received results of arecently defined search. A visual display 211 shows four destinations ofinterest, identified as 202, 204, 206 and 208. They have been ranked interms of their journey time (and not distance) from the location ofmobile device 101 and actual journey times are displayed which, inascending order, are shown as 201, 203, 205 and 207.

Details of the starting location may be supplied automatically from themobile device or entered by a user.

FIG. 3

A protocol diagram illustrating operations performed within theenvironment of FIG. 1 is shown in FIG. 3. In this example, user device101 makes a request at first communication 301 for a location-basedsearch to be performed by the first service provider server 107. Server107 returns data as a second communication 302 representing a graphicaluser interface inviting a user to specify preferences in relation to theservice being requested. Thus the request may be to locate a vendor of aparticular type that is the shortest journey time from the user'spresent location or a selected location.

Data is entered by the user which is returned as communication 303 tothe service provider 107. The service provider 107 parses the requestfor the search to be prioritised in terms of journey time the mode oftransport.

Candidate destinations are selected based on the available criteria.Each candidate is given an identification which is conveyed as fourthcommunication 304 to the service enhancing server 109, along with gridreferences (latitude and longitude) of each identified candidate, andthe grid reference of the starting position.

The service enhancing server 109 now has details of a starting positionand the location of one or more candidate destinations. In thisembodiment the service enhancing server does not need to know the natureof the destination candidates.

Using procedures detailed herein, the service enhancing server 109returns data as a fifth communication 305 back to the first serviceprovider server 107 identifying each candidate, along with a calculatedjourney time.

The journey time data is processed by the first service provider 107 toprovide meaningful search result data as a sixth communication 306 backto the user, that includes the journey time information. This data isprovided quickly, and represents valid journey time values that areperceivably more useful than mere distances.

FIG. 4

Operations performed by the service enhancing server 109 are shown inFIG. 4. The operations provide for the generation of output dataidentifying travel times to a plurality of candidate destinations from apreviously specified starting position. Furthermore, having identified amaximum travel time, it is possible for further searching to beconducted with different criteria identifying different destinationtypes but all lying within the originally defined maximum travel time.

When a search is being performed, coordinates are received identifying astarting location. A maximum travel time is also identified for anassumed mode of transport or alternatively a specific mode of transportmay be defined. Processed graph data is read that comprises graph nodesrepresenting pre-filtered map features and edges representing traveltimes between said graph nodes. A temporary graph is built of selectednodes that can be reached via selected edges within the maximum traveltime. Having constructed the temporary graph, of temporary nodes andtemporary edges, candidate destinations may be processed, by each ofthese being tested with reference to the temporary graph data.

Thus, before a search can be conducted, in an embodiment, apre-processing step of generating the graph data is performed. Asillustrated at step 401, updated map data may be identified as an XMLfile. This map data may define any geographical area. For manyapplications, the map data represents large urban areas, such as cities.The applicant has found that XML files of this type are available formost geographical areas. However, in addition to the informationrequired for the present purpose, map data of this type also includeslarge amounts of additional data that is not required.

The XML file of map data will show roads, footpaths, overground railwaysand subway railways. When travelling, it is possible for a journey to bemade using different modes of transport. In an embodiment, journey timesmay be provided with respect to walking, travelling by road andtravelling by subway trains. In an alternative embodiment, travel timesmay also be calculated for cycling, bus travelling and overground traintravelling. In an embodiment, nodes represent map features selected fromoptions comprising road intersections, bus stops, bicycle parks, railwaystations, underground stations and vehicle charging stations. Thus, inan embodiment, travel times could be provided for travelling betweenelectric vehicle charging posts.

At step 402, the XML file of map data is processed to create graph data.The graph data defines graph nodes with edges connecting these nodesthat record travel times between nodes.

At step 403 two-dimensional tree data is produced by a process of binaryspace partitioning, as detailed in FIG. 10, to allow nodes to beselected from input data identifying co-ordinates. Thus, stages 401 to403 represent pre-processing stages that create temporary datastructures to facilitate rapid and accurate searching in real time.

Having created the temporary data, the system waits for a request atstep 404. Upon receiving a request for a search, the search itself isperformed at step 405. Thus, having received data identifying a startinglocation and a plurality of candidate destinations, data is returnedidentifying travel times from this starting location to each of thesecandidate destinations.

At step 406 a question is asked as to whether another search is requiredand if answered in the affirmative a further search is performed at step405.

If another search is not required, a question is asked at step 407 as towhether the data is to be updated. If answered in the affirmative,updated map data is again identified at step 401 and appropriatetemporary data is created. If the question asked at step 407 is answeredin the negative, the system waits for the next search request at step404.

FIG. 5

Data defining the details of a map may be downloaded from availablesources in a database form, as illustrated in FIG. 5. Data of this typeis often available via an application program interface (API) tofacilitate the inclusion of geographic references within otherapplications. The data is not stored, transmitted or manipulated ingraphical form but, for ease of illustration, it is shown in graphicalform in FIG. 6. This differs from the “graph” shown in FIG. 7; thelatter having attributes consistent with graph theory.

Known and available map data comprises data arranged in three tables,specifically: a node table 501, a way table 502 and a way-node table503. The node table 501 includes a first column 504 for a nodeidentification (ID), a second column 505 for a latitude value (lat) anda third column 506 for a longitude value (long). Thus a first ID 507 islocated at a first location (lat 508, long 509) and a second ID 510 islocated at a second location (lat 511 and long 512). The node data justrepresents interesting locations in the geography.

The way table 502 specifies the nature of the roads and othertransportation routes. This includes travel speed, from which journeytimes may be assessed, without detailing an actual location. A firstcolumn 513 identifies a way ID, a second column 514 provides a name anda third column 515 includes tags. In some data-sets, an additional tagtable is included to define further attributes of a tag.

A first way 516 has a first name 517 and a first tag 518. Similarly, asecond way 519 has a second name 520 and a second tag 521. The firstname 517 and the second name 520 could be the same, representing thesame road name that extends on both sides of a junction. For majorroads, usually identified by a route number, the name could occur manytimes.

The way-node table defines the overall topology by relating the ways tothe nodes. A first column 522 defines a node ID and a second column 523provides a way ID. Thus a way, having way ID 526, starts at node 525.Subsequent nodes 527, 528, 529 are specified in a position column 524.Thus the table 503 of way-nodes identifies a node ID and a way ID, alongwith locations that sequentially define a path.

FIG. 6

Within the system, in order to configure the computer servers andprogrammable handheld devices to operate in an enhanced technical way,the data is stored numerically; as illustrated in FIG. 5. From this,graph data is generated that is also stored numerically. However, forthe purposes of illustration, a small example of map data is shown as amore conventional looking map in FIG. 6.

For the purposes of this example, the map illustrated in FIG. 6 showsconnected road, that are relevant for calculating travel times whenwalking or when travelling by road. In an embodiment, the geography mayalso be considered with respect to travelling by overground train orsubway train and an alternative train network will be displayed.However, whether the nodes represent road intersections or railwaystations, the subsequent processing to produce graph data issubstantially similar. Thus, for the purposes of this example, the roadrelated map will be described that will be considered as definingpotential graph nodes for the subsequently generated graph data.

Map nodes 601 to 637 are connected by ways; ways 641 to 646 areidentified in FIG. 6. From this small example it can be seen that for anarea of interest, such as a city, the volume of map data becomes large.Many of the nodes do not contain data that is relevant to travel timecalculations and many consecutive ways will have similar travellingproperties.

A problem therefore exists in terms of how to configure the technicalenvironment to process the available data in order to provide usefultravel-time related output in a realistic time-frame using a realisticprocessing overhead.

In addition to the route data described above, the map data alsoincludes other geographical features. In this example, these includebuildings 647 to 654, along with a pond 655.

FIG. 7

Procedure 402 for processing the map data to produce graph data sets isdetailed in FIG. 7. At step 701 non-route features are removed from themap data. In this example, this would include buildings 647 to 654 andthe pond 655 etc. Any geographical feature that does not relate totravelling by any of the modes of transport under consideration is notrequired and is therefore removed in an embodiment in order to reducedata volume.

At step 702 a mode of travel is selected. In an embodiment, three modesof travel are considered in turn, namely, walking, travelling by roadand travelling by subway train. Other modes could be included. Thus, inthis example, the process is repeated three times to produce threedistinct data sets. The topology of the data sets for walking ortravelling by car will be similar but account will be taken of the factthat one way streets may exist and some paths may be accessible only bywalking. Similarly, it will be understood that freeways would only beaccessible to motor vehicles. For the purposes of this example, thewalking example will be considered in detail.

At step 703 a path is selected and at step 704 a map node on theselected path is selected. At step 705 travel speed and distance to thenext map node (selected at step 704) is considered in order to calculatea journey time (for the particular mode of travel under consideration).At step 706 the journey time is accumulated for the particular pathselected at step 703.

At step 707 a question is asked to whether another map node is to beconsidered and when answered in the affirmative the next map node isselected at step 704.

If the question asked at step 707 is answered in the negative, aquestion is asked at step 708 as to whether another path is to beconsidered. When answered in the affirmative, the next defined path isselected at step 703.

If the question asked at step 708 is answered in the negative, aquestion is asked at step 709 as to whether another mode of travel is tobe considered. If answered in the affirmative, the next mode of travelis selected at step 702.

FIG. 8

A representation of the map data of FIG. 6 is shown in FIG. 8, after theapplication of step 701 in order to remove non-route features. Aspreviously described, a travel mode is selected at step 702 and on afirst iteration the walking mode of travel will be selected. For thepurposes of this example, a walking speed of three miles per hour isassumed from which, given a particular distance, it is possible tocalculate a travel time.

In an embodiment, when considering the geography, subsequent steps areperformed by initially selecting intersections from the top left cornerand working towards the bottom right corner until all of the paths havebeen considered. Thus, following this approach, a first intersection 601will be identified. This defines a path to a second intersection 604,therefore a travel time can be calculated between the first intersection601 and the second intersection 604.

At step 704 the next map node is selected which, in this example, willbe node 602. From the map data, the distance between map node 601 andmap node 602 is known therefore it is possible to calculate a journeytime. Thus, a journey time is calculated at step 705 and accumulated atstep 706. The question asked at step 707 will then be answered in theaffirmative resulting in node 604 being selected. Again, the journeytime is calculated from map node 602 to map node 604 and the journeytime from map node 601 to map node 604 is accumulated.

For the path under consideration, the question asked at step 707 will beanswered in the negative resulting in the next path being selected atstep 708. Thus, on the next iteration a journey time from map node 604to map node 603 will be calculated. Next, a journey time from map node604 to map node 606 may be calculated, taking account of map node 605.Similarly a journey time from map node 604 to map node 610 will takeaccount of the individual steps through map node 608 and map node 609.

The topology of the resulting graph will be dependent upon theintersections, that are treated as graph nodes. Map nodes that do notrepresent intersections, such as map node 641, provide an importantfunction of defining the distance of the way or path under considerationand as such provide for the accurate calculation of journey time.However, having accumulated journey times between intersections, theseintermediate map nodes are no longer required.

FIG. 9

A graph data set is illustrated in FIG. 9, derived from the processedmap data of FIG. 8 by means of process 402. As can be seen in theexample, map node 601 has been retained as graph node 901 which thenconnects with graph node 904, derived from map node 604. An edge 951connects graph node 901 with graph node 904 and has data associatedtherewith representing a travel time between graph node 901 and graphnode 904. Similarly, graph nodes 903, 906, 907, 911, 910, 915, 919, 912,932, 923, 937, 931, 930 and 928 have been produced from similarlynumbered (less 300) map nodes, as shown in FIG. 9.

The graph nodes shown in FIG. 9 are connected by edges, such as edge 952connecting graph node 915 with graph node 919. A travel time isassociated with edge 952 representing the time taken to travel betweennode 915 and node 919 using the selected mode of travel. Thus, in anembodiment, a graph data set of the type shown in FIG. 9 is generatedfor travelling by car, a second graph data set is generated fortravelling on foot and a third graph data set is generated, with adifferent topology, for travelling by subway train.

In an embodiment, the data associated with the edges does not representan absolute travel time but represents a variable travel time. Thus, theedges may represent variable travel times between adjacent nodes thatare dependent upon a temporal component derived non-exclusively from oneor more of the following, comprising: time of day, day of the week, timeof the year and special activity periods. A temporary graph, asdescribed with respect to FIGS. 22 and 23, is then built with referenceto a time of travel so as to account for the temporal component.Furthermore, in an embodiment, it would also be possible for real-timeupdates to be considered, such as those generated in response toaccidents or other events.

The availability of public transport will tend to vary dependent uponthe time of day and the day of the week. Modifications may also occurduring holiday periods and special activity periods, such as when majorsporting events take place in the locality.

FIG. 10

Procedures 403 for producing two-dimensional tree data are detailed inFIG. 10. In this example, a binary space partitioning tree datastructure is produced by dividing a region of interest repeatedly untileach sub region contains only one of said graph nodes. A worked exampleimplementing the procedures of FIG. 10, acting upon the graph of FIG. 9,is described below with reference to FIGS. 11 to 16, resulting in thegeneration of an example of a binary space partitioning tree as shown inFIG. 17.

At step 1001 existing regions are identified and at step 1002 a regionis selected. At step 1003 a question is asked as to whether more thanone node exists within the region and when answered in the affirmativethe region is divided in a binary fashion to create two leaves.

In an embodiment, the region of interest has been bounded and positionswithin the bound of region may be specified by Cartesian coordinates inthe x direction and in the y direction. When divisions occur, thedividing line may be expressed as being equal to one of these dimensionsbeing constant. Thus, divisions may occur along lines of constant y on afirst iteration, followed by divisions along the lines of constant x ona second iteration.

After performing the division at step 1004, a question is asked at step1006 as to whether another region is to be considered and when answeredin the affirmative the next region is selected at step 1002.

When all of the regions have been considered, the question asked at step1006 will be answered in the negative, whereafter a question is asked atstep 1007 as to whether all of the leaves have been frozen.

Referring back to step 1003, a question is asked as to whether more thanone node exists within the region and, as previously stated, whenanswered in the affirmative, a division occurs at step 1004.Alternatively, if the question asked at step 1003 is answered in thenegative, to the effect that only one node does exist within the region,the leaf is frozen at step 1005. Thus, as further and further divisionsoccur, eventually only one exclusive node will exist within each region,resulting in the question asked at step 1007 being answered in theaffirmative to the effect that all of the leaves have been frozen.

Before this situation occurs, the question asked at step 1007 will beanswered in the negative, to the effect that not all of the leaves havebeen frozen, whereafter the orientation of division is changed at step1008. Thus, after divisions along lines of constant y, for example, thechange of orientation specified at step 1008 will result in furtherdivisions occurring along lines of constant x.

In response to the question asked at step 1007 being answered in theaffirmative, to the effect that all of the leaves are frozen, the treeis considered to be complete at step 1009, resulting in the generationof a data structure as represented in FIG. 17.

FIG. 11

The graph of FIG. 9 is shown in FIG. 11. A bounded region 1101R has beendefined, such that all of the nodes are contained within region 1101Rand all activities directed towards generating travel time data will beconducted with respect to positions contained within region 1101R.

Following the procedures identified in FIG. 10, region 1101R will beidentified at step 1001 and selected at step 1002. The region containsmany nodes therefore the question asked at step 1003 will be answered inthe affirmative and the region 1101R will be divided.

FIG. 12

As shown in FIG. 12, region 1101R has been divided into a first region1201R and a second region 1202R. This represents the whole of theregions under consideration therefore the question asked at step 1006will be answered in the negative. All of the leaves have not been frozen(none of the leaves have been frozen at this stage) therefore thequestion asked at step 1007 will be answered in the negative and theorientation will be changed at step 1008. At step 1001, first region1201R is identified, along with second region 1202R.

At step 1002 region 1201R is selected and the question asked at step1003 is answered in the affirmative, to the effect that more than onenode exists within the region, resulting in the region being dividedvertically. The actual position of the division may be selected in orderto balance the number of nodes contained on either side of the divisionand many algorithms are known for providing varying degrees of balance.In many known algorithms, tradeoffs exists in terms of balancingoptimisation and speed of execution. In this example, the proceduresdescribed are effectively pre-processes performed in order to allow anenvironment to be created which can then be used for online searching.Thus, the first stages of pre-processing may be optimised and do notnecessarily have to be performed quickly because they are preformed as aone off pre-process. However when actual online searching is beingperformed, this trade-off shifts to the opposite extreme, in that speedof execution becomes preferred and measures are encouraged that reduceoverall processor overhead.

To continue with this example, the question asked at step 1006 will beanswered in the affirmative resulting in region 1202R being selected atstep 1002 and again divided at step 1004.

FIG. 13

The subdivision of region 1201R results in the creation of a firstregion 1301R and a second region 1302R. The division of region 1202Rresults in the creation of a third region 1303R and a fourth region1304R. None of the leaves have been frozen therefore the orientationwill again change at step 1008 resulting in the first, second, third andfourth regions being identified at step 1001 and the first region 1301Rbeing selected at step 1002. Further divisions occur, this time alonglines of constant y.

FIG. 14

Following this further iteration, region 1301R has been divided into afirst region 1401R and a second region 1402R. Region 1302R has beendivided into a third region 1403R and a fourth region 1404R. Similarly,region 1303R has been divided into fifth region 1405R and sixth region1406R. Region 1304R has been divided into seventh region 1407R andeighth region 1408R. At this stage, none of the leaves have been frozenbut it should be noted that region 1405R and region 1407R both onlycontain one node. Thus, the orientation is again changed at step 1008 toperform further divisions along lines of constant x.

FIG. 15

Having identified regions at step 1001, region 1401R is selected anddivided to create a first region 1501R and a second region 1502R.Similarly, region 1402R is divided to create region 1503R and region1504R. Region 1403R is divided to create region 1505R and region 1506R.Region 1404R is divided to create region 1507R and region 1508R. Region1405R is frozen because the question asked at step 1003 is answered inthe negative. Region 1406R is divided to create region 1509R and region1510R. The question asked at step 1003 is again answered in the negativewhen considering region 1407R therefore this region is frozen. Whenregion 1408R is selected this is divided to create region 1511R andregion 1512R.

FIG. 16

Upon the next iteration, most of the leaves are identified as beingfrozen. However, region 1503R is divided into region 1601R and region1602R and region 151 OR is divided into 1603R and region 1604R.

Upon the next iteration, regions 1601R, 1602R, 1603R and 1604R will befrozen. Thereafter, all of the regions will be identified as frozen andthe space will have been fully divided.

FIG. 17

The execution of the procedure shown in FIG. 10 and as illustrated byexample with reference to FIGS. 11 to 16, results in the generation of abinary space partitioning tree data structure. An example of such a datastructure is illustrated in FIG. 17, reflecting the geometry shown inFIG. 16. Each region containing only one node, as shown in FIG. 16, hasa respective frozen leaf in FIG. 17. Thus, the frozen leaves areidentified as 1501L, 1502L, 1601L, 1602L, 1504L, 1505L, 1506L, 1507L,1508L, 1405L, 1509L, 1603L, 1604L, 1407L, 1511L and 1512L. Workingbackwards up the tree, frozen leaves 1501L and 1502L make up region1401R, as shown by branch 1401L. This in combination with branch 1402Lmake up branch 1301L. Similarly, branch 1301L with branch 1302L make upbranch 1201L which in combination with branch 1202L makes up thetotality of the space, represented as branch 1101L.

The tree is used to identify, (for any particular coordinate locationwithin the region 1101R) its sub region, as identified by a frozen leaf.For the purposes of this example, a starting location 1605 is identifiedin FIG. 16. Thus, the coordinate location of starting position 1605 isknown but a question arises as to which sub region does it belong.

At branch 1101L a decision is taken as to whether the starting location1605 lies within branch 1201L or branch 1202L. Within each branch,ranges are specified in the x dimension and in the y dimension; that arecompared against the coordinate location of starting location 1605. Thusit falls within branch 1201L and then within branch 1301L, and thenwithin branch 1402L and finally within frozen leave 1504L. Thus, it canbe appreciated that a substantial overhead exists in terms of creatingthe tree structure of FIG. 7. However, during online operation, when itbecomes necessary to identify the smallest region to which a locationbelongs, the binary space partitioning tree approach allows thisevaluation to be done substantially quicker.

FIG. 18

Each smallest region shown in FIG. 16 is associated with a singleexclusive node within the overall graph data. Thus, for example, node923 is the only node within region 1407R. The table shown in FIG. 18allows the associated node to be identified, having identified theregion of interest. Thus, if a location of interest falls within region1407R, the table 1801 identifies node 923 associated with this region.

To achieve this, a first column 1802 identifies regions and a secondcolumn 1803 identifies their associated nodes. Thus, a quick lookup isprovided in order to identify associated nodes when this information isrequired.

FIG. 19

Having generated the data structures, primarily consisting of the graphdata sets and the two-dimensional tree data, it is now possible toperform a search, as identified at step 405.

In an embodiment, travel time data is generated by receiving coordinatesfor a starting location, receiving a maximum travel time and readingprocessed graph data, comprising nodes representing pre-filtered mapfeatures and edges representing travel times betweens said nodes. Thesetravel times may be set, or the travel times may be dependent upon atemporal component. A temporary graph is built of selected nodes thatcan be reached via selected edges within the maximum travel time.Candidate destinations are received and the travel time to eachcandidate destination is tested with reference to the temporary graph.

A start location is received at step 1901 which, for the purpose of thisexample, may be considered as starting location 1605. A question isasked at step 1902 as to whether this starting location can be acceptedand when answered in the negative, it is not possible for the search tobe performed resulting in the question at step 406 being asked as towhether another search is to be performed.

If the question asked at step 1902 is answered in the affirmative, dataidentifying the maximum travel time is received at step 1903. Thus, forexample, if walking, a maximum travel time of ten minutes may bespecified or if using public transport a maximum travel time of fortyminutes may be specified. However, in an embodiment, all candidateslying within this travel time are identified and these may be ranked soas to identify the candidate destination that will take the least amountof time to reach by the selected mode of transport or transportationsavailable. Again, a question is asked at step 1904 as to whether themaximum travel time is considered to be acceptable. In an embodiment,the travel time may be rejected if it is ridiculously low, say less thanthirty seconds or ridiculously high say more than six hours. However,these limits may be adjusted dependent upon the geography and theavailable modes of transport.

In an embodiment, the evaluations are sensitive to temporal factorstherefore at step 1905 the start time is received. In an embodiment,these start times may be read from a local clock or alternatively, astart time may be specified by a user on the basis that they wish tocommence the journey after a predetermined delay. At step 1906 aquestion is asked as to whether the start time is accepted and again thesearch is terminated if the start time is not considered to beacceptable. In an embodiment, for example, a start time that is morethan six hours into the future may be considered unacceptable.

Having received an acceptable starting location, an acceptable maximumtravel time and an acceptable start time, a temporary graph is built atstep 1907. Having built the temporary graph, it is now possible toreceive candidate destinations and from this populate a list.

At step 1908 a candidate destination is received and a question is askedat step 1909 as to whether the destination is acceptable. If answered inthe negative, the candidate is rejected and the next candidate isconsidered, when received at step 1908.

If the question asked at step 1909 is answered in the affirmative, thecandidate is added to a candidate list at step 1910 and a question isthen asked at step 1911 as to whether another candidate is to beconsidered. Thus, when the question asked at step 1911 is answered inthe affirmative, the next candidate is received at step 1908. When thequestion asked at step 1911 is answered in the negative, to the effectthat no further candidates are to be considered, the list is sorted atstep 1912 in order of shortest travel time.

FIG. 20

Procedures 1902 for judging the acceptability of a start location aredetailed in FIG. 20. The coordinates of an actual starting location aretransformed to a modified origin at the location of a node in theprocessed graph data. Furthermore, a starting location may be rejectedif the actual location is too far away from its respective modifiedorigin. Thus, in an example, the starting location may be rejected andhence the search cancelled, if the actual starting location is more thanthree hundred feet away from the modified origin.

At step 2001 a region is located from the tree of FIG. 17. The startinglocation 1605 is identified as being in region 1504R. Referring to table1801 of FIG. 18, this results in the starting location 1605 beingtranslated to modified origin 904. Thus, a graph node is allocated atstep 2002.

At step 2003 the distance from the allocated node or modified origin tothe actual starting location is calculated and a question is then askedat step 2004 as to whether the actual distance is smaller than a maximumdistance. If answered in the affirmative, the search continues but ifanswered in the negative, to the effect that the distance is larger thanthe maximum allowed distance, the search terminates.

In the example described, the retained nodes, that is those present inthe graph data, are present because they represent major geographicalfeatures such as road interchanges or railway stations. If these areadopted as the only graph nodes, it is possible that there will be aninsufficient number of graph nodes within the overall geography,resulting in the smallest leaf regions being too large and too manysearches being rejected. Thus, in an embodiment, it may be possible toadopt other features which in turn become graph nodes and therebyincrease the number of frozen leaf regions present within the geographyso as to reduce the overall size of each of these regions and therebyaccommodate an optimum number of searches. This may be considered as a“grade of service” parameter which, for example, may specify that thefragmentation of the regions should be such as to ensure that at leastninety-five percent of search requests are satisfied.

FIG. 21

Procedures 1907 for building a temporary graph are detailed in FIG. 21.Starting from the origin, at step 2101 an edge is selected, connectingthe origin to a first node. A maximum travel time is known and a traveltime from the origin to the selected node is known, via the edgeselected at step 2101, therefore the travel time for the edge issubtracted from the maximum travel time. A question is asked at step2103 as to whether any time remains, that is to say, the result of theprevious subtraction remains positive. Thus, if the question asked atstep 2103 is answered in the affirmative, the node is retained at step2104. Thus, in this way, the node selected from the graph of FIG. 16 isadded to the build of the temporary graph, as illustrated in FIG. 22.

A question is then asked at step 2105 as to whether another node ispresent along the selected edge and when answered in the affirmative,the node is selected and the time taken to travel to this node isdeducted at step 2102. Again, at step 2103 a question is asked as towhether time remains and on this occasion, for example, the node may bebeyond the allowed maximum travel time thereby resulting in the questionasked at step 2103 being answered in the negative. Following this, thequestion is again asked at step 2106 as to whether another edge ispresent.

FIG. 22

An example of a temporary graph is shown in FIG. 22. In the previouslydescribed example, an actual starting location is identified as location1605 in FIG. 16. This lies within region 1504R (determined by use of thetree structure of FIG. 17) which in turn contains node 904, determinedby reference to table 1801 of FIG. 18. Node 904 therefore represents thestarting location for the temporary graph, identified as 904T in FIG.22. Referring back to FIG. 16, a first edge is selected which may be theedge connecting node 904 to node 901. An assessment is made to theeffect that it is possible to travel to node 901 within the maximumtravel time therefore node 901 is retained and is shown as node 901T inthe temporary graph of FIG. 22.

Further iterations of the procedures shown in FIG. 21 result inconsiderations being made with respect to the edges extending to nodes903, 906 and 910 etc. Thus, for the purposes of this example, it ispossible to reach node 903, therefore this is retained and built intothe temporary graph as node 903T. Similarly, node 906 is retained astemporary node 906T and, on a first iteration it is found possible toretain node 907 and by a further operation it is possible to retain node915. Thus, respectively, these are retained and built into the temporarygraph as node 907T and node 915T. Similarly, node 910 is retained asnode 910T, node 911 is retained as node 911T and node 912 is retained asnode 912T. Thus, the temporary nodes shown in FIG. 22 represent thenodes where it is possible to travel to within the maximum allowedjourney time. For all of the other nodes identified in FIG. 6, thenecessary journey time would be longer than the maximum permitted. Thus,these are not built into the temporary graph.

For the purposes of this example, candidate destinations are shown atlocations 2201, 2202 and 2203. The procedure of FIG. 19 now determineswhether these candidate destinations may be accepted and then ranks themin terms of journey time.

It can therefore be appreciated that an embodiment of the inventionprovides a data structure that comprises selected nodes that can bereached via selected edges within a specified maximum journey time. Thedata structure is built from processed graph data, as shown in FIG. 16,and the processed graph data comprises nodes that represent pre-filteredmap features, as shown in FIG. 6, and edges related to travel timesbetween nodes. In an embodiment, the data structure is built dynamicallyin response to a search request, wherein the travel times between nodesare time and event sensitive.

FIG. 23

Procedures 1909 for determining whether a candidate destination may beaccepted are detailed in FIG. 23. In an embodiment, the procedures ofFIG. 23 are conducted as soon as details of a candidate destination havebeen received. Thus, these procedures may take priority over thebuilding of the temporary graph structure in FIG. 22. The actualmechanism for achieving this will be dependent upon the nature of theprocessing environment. Thus, incoming data representing a candidatedestination may create an interrupt so as to halt activities beingconducted elsewhere. The other activities, possibly the generation of atemporary graph structure, could also be seen as a background activity,with the processing of incoming candidate destinations being identifiedas a foreground activity and thereby having a higher priority. In someenvironments, it may be possible to multi-thread these applications andwith an appropriate hardware platform, it may be possible to perform adegree of parallel processing.

At step 2301 a calculation is made as to the actual distance of thecandidate destination from the origin. This particular step does notmake any reference to travel times but acts as a quick, crude filter toreject candidate destinations that clearly could not be reached withinthe travel time specified. Thus, if a candidate destination isconsidered to be too far away from the origin, the question asked atstep 2302 is answered in the affirmative and the candidate is rejected.

If the question asked at step 2302 is answered in the negative, theregion containing the candidate is located at step 2303. Thus, againreference is made to the tree structure of FIG. 17 and the table of FIG.18. Thus, at step 2304 the relevant node is identified and at step 2305a calculation is made to determine the distance between the location ofthe actual candidate and the location of its associated node. If thisdistance is considered to be too far, a question asked at step 2306 willbe answered in the affirmative and again the candidate will be rejected.In an embodiment, this distance may be adjusted and, as an illustration,a distance of, say, three hundred feet may be selected.

If the question asked at step 2306 is answered in the negative, to theeffect that the candidate destination is close enough to the node, theactual node is assumed to be the destination and the candidate isaccepted at step 2307. Thus, as previously described, after acceptance,the candidate is added to a candidate list at step 1910 and this list isthen sorted at step 1912 in order to present a journey time list to auser as illustrated in FIG. 2.

FIG. 24

In addition to selecting a preferred candidate from a relatively shortlist, as shown in FIG. 2, a substantially larger group of candidates maybe displayed graphically. The graphical display of FIG. 24 has distinctimprovements over a conventional isochronal representation. It is drivenwith respect to specific candidates of interest. Thus, the relevantinformation is clear and accurate. Furthermore, the computationaloverhead is reduced and the procedures involved focus the processingcapabilities on the particular candidates of interest.

In FIG. 24, graphical display 2401 has a width 2402 and a height 2403.The area displayed is scaled to represent a geographical area ofinterest and the travel time related data may be placed over aconventional map of the area, possibly showing rivers and major streetsetc.

In the example, an origin 2404 is shown. Several points are also shownrepresenting candidates of interest that have a substantially similarjourney time from origin 2404. In the example, four points 2405 areclose. Three further groups 2406, 2407 and 2408 are shown. In anexample, it may be possible, without private transport, to reach all ofthe points within ten minutes.

With reference purely to the geographical data, group 2408 may have beenperceived as being too far away. However, this group may be close to aregular bus route or subway station and as such travel times aresubstantially reduced. Thus, group 2408 has been included in the outputdata set.

The invention claimed is:
 1. A method of generating travel time data,comprising the steps of: receiving coordinates for a starting location;receiving a maximum travel time; reading processed graph data comprisingnodes representing pre-filtered map features and edges representingtravel times between said nodes; building a temporary graph of selectednodes that can be reached via selected edges within said maximum traveltime; receiving candidate destinations; and testing the travel time tosaid candidate destinations with reference to said temporary graph,wherein coordinates of each candidate destination are transformed to amodified destination at the location of a node in said processed graphdata, wherein coordinates of each candidate destination are transformedwith reference to a binary space partitioning tree data structureproduced by dividing a region of interest repeatedly until eachsub-region contains only one of said graph nodes.
 2. The method of claim1, wherein said edges represent variable travel times between adjacentnodes that are dependent upon a temporal component derived fromnon-exclusively one or more of the following, comprising: time of day,day of the week, time of the year and special activity periods; and saidtemporary graph is built with reference to a time of travel so as toaccount for said temporal component.
 3. The method of claim 1, whereincoordinates of an actual starting location are transformed to a modifiedorigin at the location of a node in said processed graph data.
 4. Themethod of claim 1, wherein each candidate destination is transformedupon arrival, in preference to said building step, thereby reducing thebuilding of said temporary graph to a background process.
 5. The methodof claim 1, wherein a candidate destination is rejected if it has alocation that is displaced from a starting location by a firstpredetermined distance.
 6. The method of claim 1, wherein a candidatedestination is rejected if it has a location that is displaced from anearest node by a second predetermined distance.
 7. The method of claim1, wherein said processed graph data is produced by processing map datato remove features that are not travel related.
 8. The method of claim1, wherein said map data is processed a plurality of times to produce aplurality of processed graph data sets, applicable to respective modesof transport.
 9. The method of claim 1, wherein a travel time for eachselected node is calculated by subtracting travel times between nodesfrom said maximum travel time.
 10. The method of claim 1, wherein saidtesting step identifies destinations that can be reached within saidmaximum travel time and returns data that identifies each candidate withan indication of travel time.
 11. The method of claim 10, wherein saididentified candidates are ranked in terms of travel time.